煤矿区城市矿物气溶胶的SEM-EDX特征分析

采集煤矿区城市义马、平顶山、永城夏季大气PM₁₀样品,采用带能谱的扫描电镜(SEM-EDX)研究了PM₁₀中的矿物颗粒组成、成因及来源。结果表明,矿区矿物颗粒按化学成分共有5种主要类型,分别为"富Si"、"富Ca"、"富S"、"富K"、"富Cl"型。其中平顶山地区"富Si"颗粒占百分比最高(78%),矿物颗粒硫酸盐化程度小;永城地区硫酸盐化程度中等,几乎所有的"富Ca"碱性碳酸盐颗粒都硫酸盐化成石膏;义马地区矿物硫酸盐化程度最大,除石膏以外,还有一定量硫酸铵形成。永城和义马地区还出现了一定量的"富K"(12.7%)和"富Cl"(10.6%)颗粒,与秸秆焚烧活动有关。通过对3个矿区城市PM₁₀硫酸盐化程度对比可以发现,偏碱性的碳酸盐矿物、煤炭燃烧和秸秆焚烧燃烧释放出大量的酸性SO₂以及较高的空气湿度,均有利于硫酸盐化的进行,硫酸盐颗粒的形成对煤矿区城市的区域性气候具有一定影响。     

天山乌鲁木齐河源1号冰川大气气溶胶的微观形貌及元素组成分析

为研究冰川区大气气溶胶单颗粒物的物理化学特征,使用带能谱的扫描电镜(SEM-EDX)对2007年在天山乌鲁木齐河源1号冰川东支积累区海拔4 130m(86°49′E,43°06′N)处采集的38个气溶胶样品中的38 861个单颗粒物进行了微观形貌和元素组成的分析.结果表明:天山乌鲁木齐河源1号冰川区大气气溶胶主要以粒径在0.6～2.5μm之间的不规则的非圆形矿物颗粒为主,其中以富含Si、Ca的粘土矿物颗粒为主,与人类活动密切相关的含S颗粒物及烟尘飞灰等含量较少.这与其它沙尘源区的气溶胶特征相似,其中含Ca颗粒多于其它沙尘源区,主要受西风带的影响.气团轨迹显示,来自于西面中亚地区的高空气流影响了1号冰川区的大气环境,表明天山乌鲁木齐河源1号冰川区的气溶胶主要代表了中亚沙尘源区对流层中上部大气的本底状况.     

拉萨市夏季大气降尘单颗粒矿物组成及其形貌特征

应用带能谱的电子扫描电镜(SEM-EDX)对拉萨市夏季正常天气下收集的大气自然沉降气溶胶样品进行分析,研究了拉萨市大气降尘矿物组成和各种物相形貌特征信息。拉萨市大气颗粒物含有硅酸盐颗粒、富钙颗粒、富铁颗粒、富碳颗粒(燃煤飞灰颗粒和燃油飞灰颗粒)和植物残体颗粒。根据颗粒物数量统计发现拉萨市大气颗粒物以硅酸盐颗粒为主,富钙颗粒和富铁颗粒次之,需要指出的是以燃油飞灰为主的富碳颗粒已占到一定比重,说明以燃油为主的机动车尾气对拉萨大气污染在加强。研究结果表明,大气降尘矿物成分及其形貌特征可以用作判定污染物来源的重要标志,拉萨大气中颗粒来源的多样性决定了治理措施也应综合进行。     

纳米比亚红沙漠沙粒特征及其成因

针对纳米比亚红色沙漠呈现红色的原因及其形成环境,借助双目镜、电子显微镜及扫描电镜等手段,统计测定了沙粒形态和矿物成分,研究了红色沙漠沙粒及其红色包裹物成分。研究表明,沙粒主要由石英(91%)、长石(4%)和岩屑(5%)颗粒组成,原岩以花岗岩为主,还有火山碎屑岩、泥岩和粉砂岩,不同类型沙粒磨圆度存在差异。由于不同含量的黏土矿物和铁氧化物附着于沙粒表面,使沙粒呈现不同程度的红色,进而导致沙漠呈现红色。黏土矿物和铁氧化物中主要元素为O、Si、Fe、Al、Mg,含少量K、Ca、Ti、Cl、P,矿物成分相当于伊利石、蒙脱石、高岭石、绿泥石、赤铁矿、针铁矿和钛铁矿等,矿物组合特征揭示了红色包裹物的形成环境以偏冷、湿润气候为主。     

大气微纳米颗粒物界面反应与矿物协同演化意义

综述了大气气溶胶颗粒物的特征、颗粒物的界面反应与矿物协同演化意义;重点介绍了大气颗粒物粒径分布和矿物成分,以及常见有毒有害气体的界面反应产物特征与关键化学过程;总结了矿物颗粒在大气气溶胶形成过程中汇聚、调控、催化的作用,以及颗粒物与大气中SO₂、NO_x的协同反应机制;分析了微纳米颗粒对二次有机气溶胶形成的影响,以及大气矿物相颗粒界面反应产物组合及协同演化作用.可为进一步研究大气颗粒物与大气中痕量污染气体反应形成二次气溶胶进而影响大气化学组成的过程提供指导,对深入探讨大气矿物颗粒表面特性在复合污染物中多介质反应的微界面化学过程,矿物尘-污染物气溶胶体系在雾-霾形成、转换、新生粒子和阻断行为的复合作用具有重要的环境学意义.      

青藏高原气溶胶单颗粒类型及粒度分布

应用场发射扫描电镜(FESEM)对青藏高原纳木错综合观测站和香格里拉本底站2011年7～8月份不同天气情况下收集的气溶胶样品进行研究。结果表明,区域内气溶胶单颗粒类型主要包括烟尘集合体、球形颗粒(焦油球、燃煤飞灰)、似球形颗粒、矿物颗粒、生物颗粒等,香格里拉的球形颗粒中出现了飞灰颗粒,而纳木错样品中没有。纳木错气溶胶颗粒的数量-粒度峰值和体积-粒度峰值分别出现在0.2～0.3 μm和1～2.5 μm,矿物颗粒数量和体积最多,分别占44.4%和61.7%。香格里拉气溶胶颗粒的数量-粒度峰值和体积-粒度峰值都呈现双峰分布,主峰均分布在>2.5 μm范围,矿物颗粒数量和体积最多,分别占51.7%和58.7%。细粒子和粗粒子分别为纳木错和香格里拉气溶胶的主要类型。纳木错气溶胶中矿物颗粒最多,数量百分比为44.4%,其次为烟尘集合体(29.5%)和球形颗粒(26.1%),香格里拉气溶胶中矿物颗粒数量百分比为51.7%,其次为球形颗粒(29%)和烟尘集合体(19.3%);纳木错气溶胶总颗粒物主要分布在0.2～0.3 μm粒径范围中,数量百分比为32.59%,其中矿物颗粒最多(15%),其次为球形颗粒(11.5%)和烟尘集合体(6.1%)。香格里拉气溶胶颗粒物主要分布在>2.5 μm粒径范围中,数量百分比为37.5%,其中矿物颗粒最多(17.9%),其次为球形颗粒(10%)和烟尘集合体(9.6%)。     

电感耦合等离子体发射光谱法同时测定卤水中锂钠钾钙镁硼硫氯

建立了电感耦合等离子体发射光谱法(ICP-AES)同时测定碳酸盐型、硫酸盐型、氯化物型三种类型卤水中Li、Na、K、Ca、Mg、B、S、Cl等高低含量元素的分析方法。选择仪器最佳的工作条件为射频功率1400W,炬管位置位于-3,载气流量0.60 L/min。确定了各元素测定谱线,使用ICP-AES的双向观测模式、轴向观测模式测定Li、Ca、B、S、Cl以及低含量的K、Mg,径向观测模式测定高含量的Na、K、Mg,可确保卤水中不同含量的元素同时检出。Li、Na、K、Ca、Mg、B、S的检测下限为0.07～3.00 mg/L,Cl的测定下限为165mg/L。方法精密度(RSD,n=10)均小于5%,回收率为92.4%～109.7%。其中Na、K、Mg、S、Cl测定结果与传统方法测定结果基本吻合。     

黔西北香炉山稀土矿的稀土元素赋存状态

以香炉山稀土矿床为研究对象,研究矿石中稀土元素赋存状态。采用扫描电镜、电子探针及化学浸取实验方法,对稀土矿石样品进行测试分析和浸取实验。扫描电镜未扫描出独立的稀土矿物,电子探针对样品原位微区探测出的元素有:O、Al、Si、Ca、Mg、Fe、Ti、K、Na、S、Cl、C、Cu、Cr、V、Pt,未探测到稀土元素。采用10%的(NH_4)_2SO_4、(NH4)Cl、NaCl和H_2SO_4化学试剂,室内常温常压,浸取24 h,结果显示,矿石中稀土元素容易被浸取,浸出率较高,为11.47%～24.00%,说明矿石中稀土元素的赋存状态为离子态存在,而不是稀土矿物。     

西峰和段家坡剖面S5-1层段磁性矿物的成分与组合特征

从西峰和段家坡黄土剖面S5-1层段中分选出<30μm粒级、磁性相对最强的组分(分别为XS-4J和DS-4J),先后进行了MPV-3光学显微镜的观察与反射率测定、矿物的扫描电镜能谱测定和X射线衍射物相分析.两个样品的磁性矿物均以风尘碎屑状的钛铁氧化物为主.XS-4J样矿物的反射率和Fe的含量都普遍较高,磁性矿物除磁(赤)铁矿、赤铁矿外还见有含铁高的氧化物(Fe 72.20%～86.70%,质量分数)和含Cr、Ni的钛铁晶石或钛铁矿.DS-4J样的磁性矿物中Fe与Ti元素呈明显的负线性相关关系,Si、Al、Ca的含量较高,矿物以磁(赤)铁矿、赤铁矿、针铁矿和褐铁矿为主,并明显见有磁性矿物被溶蚀和新生的磁(赤)铁矿.磁性矿物成分与组合特征的差异反映了西峰与段家坡S5-1岩石中磁性矿物的物质来源与保存条件有较明显的差异.     

北京市春夏季大气气溶胶的单颗粒分析表征

采集了北京市2000年春夏季大气气溶胶样品5个，采用扫描电镜X射线能谱技术分析大气气溶胶单颗粒约2500个。研究结果表明，沙尘期间，矿物尘是最主要的颗粒物种类，非沙尘期间，北京市大气气溶胶中主要检出矿物尘和含硫颗粒物。夏季随着颗粒物污染的加重，含硫颗粒物的数目百分数增加。是北京市大气颗粒物污染的重要特征。重点讨论了Ca-S颗粒、K-S颗粒和Ca-K-S颗粒三类典型含硫颗粒物的化学组成和粒径分布特征。数目可观的Ca-K-S颗粒以及其他硫酸盐颗粒的生成与相对湿度和云量等气象条件相关，这些颗粒物可能是云中过程的产物。减少SO2排放，减少含硫颗粒物，对于控制北京市的大气颗粒物浓度水平具有重要意义。     

庐江陨石的化学组成

庐江陨石是一块落的球粒石陨石,本文详细介绍了庐江的化学全分析,铁物相,镍物相和微量元素分析方法,给出了庐江陨石的主要元素组成和微量元素组成特征。由此可以确定该陨石的化学群属于ＬＬ群。     

Melting relations and major element partitioning in an oxidized bulk Earth model composition at 15–26 GPa

Melting experiments were performed on an FeO-rich bulk Earth model composition in the CMFAS system in order to investigate the partitioning of major elements between coexisting minerals and melts. The starting material (34.2% SiO₂, 3.86% Al₂O₃, 35.2% FeO, 25.0% MgO and 1.88% CaO), contained in Re-capsules, was a mixture of crystalline forsterite and fayalite, and a glass containing SiO₂, Al₂O₃, and CaO. Olivine is the first liquidus phase at 10 GPa but is replaced by majoritic garnet (ga) in the 15–26 GPa range. Magnesiowüstite (mw) crystallizes close to the liquidus and is joined by perovskite (pv) at 26 GPa.

The quenched melt compositions are homogeneous throughout the melt region of the charges and are only slightly enriched in Si, Ca and Fe, and depleted in Mg, relative to the starting composition. The Fe/Mg and Ca/Al ratios in all of the minerals increase rapidly below the liquidus to become compatible with the bulk composition at the solidus. At 26 GPa, a relative density sequence of mw>pv>melt>ga is observed. This indicates that majorite floating, combined with the sinking of magnesiowüstite and perovskite can be expected during the solidification of a Hadean magma ocean and in hot mantle plumes early in the Earth's history. The mineral–melt partitioning relations indicate that fractional crystallization or partial melting in the transition zone and the upper part of the lower mantle would increase the Fe/Mg and Ca/Al ratios of the melt, even if magnesiowüstite was predominant in the solid fraction. A significant contribution of accumulated mw to the segregation of the protocore is therefore unlikely. The suggested process of perovskite fractionation to the lower mantle is not capable of increasing the Mg/Si ratio in the residual melt, and the combined fractionation of perovskite and magnesiowüstite produces a melt with elevated ratios of Si/Mg, Ca/Al and Fe/Mg.     

Characterisation of aerosol from Santiago,Chile: an integrated PIXE–SEM–EDX study

Santiago de Chile is a big city with huge air quality problems, being one of the most polluted cities in the world. This is aggravated during winter by the topography and meteorological conditions of the city. Although public policies have been developed to minimise the atmospheric aerosol pollution, there is a lack of adequate knowledge and poor characterisation of these aerosols (in its PM_2.5 and PM₁₀ fractions). In this study we sampled atmospheric particles during winter in two distinct areas of Santiago: downtown (Teatinos Street) and in a more residential area (Macul). Major (Si, Al, Fe, Ca and K) and some trace element (S, Cl, Ti, P, Cr, Cu and Zn) compositions were obtained by proton-induced X-ray emission (PIXE). Morphological, type and chemical characterisation was also performed using scanning electron microscopy (SEM) coupled with an energy dispersive X-ray microanalysis system (SEM–EDX). Besides the carbon particles, the contribution of which can be quite important in the atmospheric aerosol, especially in downtown, unambiguously lithogenic (i.e. of geological origin) particles and elements are the second highest contributors. Enrichment factor calculation, together with particle identification and element correlation allow the origin of some elements and particles to be traced, revealing anthropogenic origins for some of them that are specific to the Santiago area.     

北京、郑州和深圳三城市空气中气溶胶单颗粒特征的扫描电镜分析

分别采集北京、深圳和郑州3个城市气溶胶样品,使用场发射扫锚电镜-能谱仪观察气溶胶单颗粒的显微形貌和元素组成,并利用图像分析系统对PM2.5的粒径进行了分析。结果表明,城市气溶胶单颗粒类型以矿物颗粒、烟尘和球形颗粒(飞灰和二次粒子)为主。对比3个城市气溶胶中不同颗粒类型数量百分比发现,矿物颗粒数量最多的城市是北京,飞灰和烟尘数量最多的城市是郑州,而规则矿物颗粒数量最多的城市是深圳。3个城市气溶胶单颗粒的数量-粒径分布均呈单峰分布。深圳气溶胶中颗粒物的粒径相对较小,其次为郑州、北京。3个城市气溶胶中颗粒物来源不同程度上都受到交通污染源影响,而燃煤源对北京和郑州气溶胶中颗粒物来源影响仍然不容忽视。     

Effect of phosphate, silicate, and Ca on the morphology, structure and elemental composition of Fe(III)-precipitates formed in aerated Fe(II) and As(III) containing water

We investigated Fe(III)-precipitates formed from Fe(II) oxidation in water at pH 7 as a function of dissolved Fe(II), As(III), phosphate, and silicate in the absence and presence of Ca. We used transmission electron microscopy (TEM), including selected area electron diffraction (SAED) and energy dispersive X-ray spectroscopy (EDX) to characterize the morphology, structure and elemental composition of the precipitates. Results from our companion X-ray absorption spectroscopy (XAS) study suggested that the oxidation of Fe(II) leads to the sequential formation of distinct polymeric units in the following order: Fe(III)-phosphate oligomers in the presence of phosphate, silicate-rich hydrous ferric oxide (HFO-Si) at high Si/Fe (>0.5) or 2-line ferrihydrite (2L-Fh) at lower Si/Fe (∼0.1-0.5), and lepidocrocite (Lp) in the absence of phosphate at low Si/Fe (<0.1). Results from this study show that the size of the polymeric units increased along the same sequence and that the aggregation of these polymeric units resulted in spherical particles with characteristic surface textures changing from smooth to coarse. The diameter of the spherical particles increased from 15 to 380 nm as the molar ratio (P + Si + As)/Fe(II) in the starting solution decreased and larger spherical particles precipitated from Ca-containing than from Ca-free solutions. These trends suggested that the size of the spherical particles was controlled by the charge of the polymeric units. Spherical particles coagulated into flocs whose size was larger in the presence than in the absence of Ca. Further observations pointed to the importance of Fe(II) oxidation and polymerization versus polymer aggregation and floc formation kinetics in controlling the spatial arrangement of the different polymeric units within Fe(III)-precipitates. The resulting structural and compositional heterogeneity of short-range-ordered Fe(III)-precipitates likely affects their colloidal stability and their chemical reactivity and needs to be considered when addressing the fate of co-transformed trace elements such as arsenic.     

广西清明山铜镍硫化物矿床上升气流微粒研究

为探讨上升气流微粒与深部隐伏矿体之间关系,在广西清明山铜镍硫化物矿床上方土壤中采集上升气流微粒,并采用透射电子显微镜(TEM)对微粒的形貌、大小、聚合状态、化学组分及结构等进行分析。结果表明,微粒主要由Cu、Co、Zn、Fe、Ca、Si、S等元素组成,其中成矿元素Cu、Co以自然Cu-Fe-Co、Zn-Fe-Co及Fe-Co合金微粒的形式存在,其余如Fe、Ca、Si、S等元素则以氢氧化物、氧化物及碳酸盐微粒形式存在。微粒可分为微粒聚合体及单个微粒,微粒的大小为50~500nm,微粒的形状多为不规则状、近椭圆形、近球状、水滴状和近长方体等。微粒中高含量的Cu、Co、Zn来源于深部隐伏矿体,含Fe、S微粒来源于矿床中金属硫化物矿物。此外,高价态的微粒组分指示微粒处于相对氧化的环境。清明山铜镍硫化物矿床的上升气流微粒组分与矿床矿物组分间存在着较好的对应性,本研究为隐伏铜镍硫化物矿床提供了新的找矿方法。     

Experimental investigation of the origin of majoritic garnet inclusions in diamonds

 Multianvil experiments were carried out at 10–15 GPa and 1600–1700 °C to match the compositions of majoritic garnet inclusions from diamonds, and to determine the compositions of other phases potentially coexisting with these inclusions in the source. Most experiments produced coexisting majoritic garnet, diopsidic clinopyroxene, one or more (Mg,Fe)₂SiO₄ polymorphs, and quenched carbonatic melt. The experimental garnets had relatively high Ca and Fe contents similar to the observed Ca and Fe contents of the inclusions. The resulting Si contents confirmed that the depth of origin of the inclusion with the highest Si content did not exceed 410 km, thus none of the majoritic garnet inclusions found so far originated in the transition zone (410–660 km). The evidence from inclusions and experiments is consistent with the presence of an eclogite layer occurring globally between 200 and 410 km. Compositional variations observed among more than 100 majoritic garnet inclusions with their Si content, which is a measure of pressure and depth, are consistent with the origin of the eclogite layer by crystal fractionation in a magma ocean. The compositions of olivine coexisting with majoritic garnet in the experimental products had the average Fe/(Fe + Mg) ratios between 0.16 and 0.28. Inclusions with such high Fe contents have not been found; the Fe/(Fe + Mg) ratio of the olivine inclusions in diamonds usually varies between 0.05 and 0.09. Hence, the mantle between 200 and 410 km may not contain olivine. In the absence of olivine, the discontinuity at 410 km is most likely a chemical boundary between the 200-km-thick eclogite layer and a more mafic transition zone. Received: 15 March 2001 / Accepted: 14 September 2001     

大麻坪地区二辉橄榄岩部分熔融实验研究

本文以采自大麻坪地区汉诺坝玄武岩中的二辉橄榄岩包体为初始实验物料,在压力1.0～3.0 GPa、温度1350～1550℃条件下进行了部分熔融实验,对实验产物进行了岩相学研究和电子探针成分分析。二辉橄榄岩在1350℃开始熔融,在实验的温度压力范围内,熔融程度为10%～30%。随熔融程度的升高,部分熔融后残余岩石倾向于向富镁、低铁、低钙、低硅的趋势演化,而部分熔融产生的熔体则倾向于富镁、富铁、低铝、低硅的趋势演化。在岩石化学图解上本次实验中二辉橄榄岩部分熔融产生的熔体化学组成与汉诺坝地区拉斑玄武岩的组成相近。随熔融程度升高,熔体具有从苦橄质→玄武质演化的趋势。     

Titanian clinohumite–garnet–pyroxene rock from the Su-Lu UHP metamorphic terrane, China: chemical evolution and tectonic implications

A garnet–pyroxene rock containing abundant Ti-clinohumite (ca. 40 vol.%) occurs along with eclogites as small blocks in quartzo-feldsparthic gneiss in the southern end of the Chinese Su-Lu ultrahigh-pressure (UHP) metamorphic terrane. It consists of three aggregates: (1) Ti-clinohumite-dominated aggregate with interstitial garnet and pyroxene, (2) garnet+pyroxene aggregate with Ti-clinohumite inclusions, and (3) Ti-clinohumite-free aggregate dominated by garnet. Apatite, phlogopite, zircon, hematite, pentlandite, and an unknown Ni-Fe-volatile-Si (NFVS) mineral, which is replaced by Ni-greenalite, occur as accessories. Serpentine is the major secondary mineral. Garnet (Prp_63.9–64.6Alm_25.8–26.9Grs_1.4–7.9Uva_0.5–7.6Sps_1.0) in all three aggregates is pyrope-rich with very low grossular component, with that in the aggregate (2) most enriched in Cr (Cr₂O₃=2.55 wt.%). Orthopyroxene is depleted in Al (Al₂O₃=0.16 wt.% in the cores) and Ca (CaO=0.06–0.09 wt.% in the cores), with X_Mg (Mg/(Mg+Fe)) values at ca. 0.900. Clinopyroxene is chromian diopside with Fe³⁺≥Fe²⁺. Matrix clinopyroxene has a lower X_Mg (0.862) than that (0.887) included in Ti-clinohumite. The rock contains modest amount of heavy rare earth elements (HREE) (10 to 12×C1 chondrite), with significant enrichment in Cr, Co, Ni, V, Sr, and light rare earth elements (LREE) (22 to 33×C1 chondrite). The clinopyroxene is very enriched in Cr (Cr₂O₃ is up to 2.09 wt.% in the cores) and Sr (ca. 350 ppm) and LREE (Ce_N/Yb_N=157.7). Ti-clinohumite is enriched in Ni (1981 ppm), Co (123 ppm), and Nb (85 ppm).

While it is possible to enrich ultramafites in incompatible elements in a subducted slab, the high Al, Fe, Ti, and low Si, Ca, and Na contents in the Ti-clinohumite rock are difficult to account for by crustal metasomatism of an ultramafite. On the other hand, the similarity in major and trace element compositions and their systematic variations between the Ti-clinohumite-garnet-pyroxene rock of this study and those of Mg-metasomatised Fe–Ti gabbros reported in the literature suggest that crustal metasomatism occurred in a gabbroic protolith, which resulted in addition of Cr, Co, Ni, and Mg and removal of Si, Ca, Na, Al, and Fe. This implies that the rock was in contact with an ultramafite at low pressure. During subsequent subduction, the metagabbro was thrust into the country gneiss, where gneiss-derived hydrous fluids caused enrichment of Sr and LREE in recrystallised clinopyroxene. P–T estimates for the high-pressure assemblage are ca. 4.2 GPa and ca. 760 °C, compatible with those for the eclogites and gneisses in this terrane. It is possible that the Ti-clinohumite-garnet-pyroxene rock and associated eclogites represent remnants of former oceanic crust that was subducted to a great depth.     

Micro-scale tracing of Fe and Si isotope signatures in banded iron formation using femtosecond laser ablation

We have detected micrometre-scale differences in Fe and Si stable isotope ratios between coexisting minerals and between layers of banded iron formation (BIF) using an UV femtosecond laser ablation system connected to a MC-ICP-MS. In the magnetite–carbonate–chert BIF from the Archean Old Wanderer Formation in the Shurugwi Greenstone Belt (Zimbabwe), magnetite shows neither intra- nor inter-layer trends giving overall uniform δ⁵⁶Fe values of 0.9‰, but exhibits intra-crystal zonation. Bulk iron carbonates are also relatively uniform at near-zero values, however, their individual δ⁵⁶Fe value is highly composition-dependent: both siderite and ankerite and mixtures between both are present, and δ⁵⁶Fe end member values are 0.4‰ for siderite and −0.7‰ for ankerite. The data suggest either an early diagenetic origin of magnetite and iron carbonates by the reaction of organic matter with ferric oxyhydroxides catalysed by Fe(III)-reducing bacteria; or more likely an abiotic reaction of organic carbon and Fe(III) during low-grade metamorphism. Si isotope composition of the Old Wanderer BIF also shows significant variations with δ³⁰Si values that range between −1.0‰ and −2.6‰ for bulk layers. These isotope compositions suggest rapid precipitation of the silicate phases from hydrothermal-rich waters. Interestingly, Fe and Si isotope compositions of bulk layers are covariant and are interpreted as largely primary signatures. Moreover, the changes of Fe and Si isotope signatures between bulk layers directly reflect the upwelling dynamics of hydrothermal-rich water which govern the rates of Fe and Si precipitation and therefore also the development of layering. During periods of low hydrothermal activity, precipitation of only small amounts of ferric oxyhydroxide was followed by complete reduction with organic carbon during diagenesis resulting in carbonate–chert layers. During periods of intensive hydrothermal activity, precipitation rates of ferric oxyhydroxide were high, and subsequent diagenesis triggered only partial reduction, forming magnetite–carbonate–chert layers. We are confident that our micro-analytical technique is able to detect both the solute flux history into the sedimentary BIF precursor, and the BIF’s diagenetic history from the comparison between coexisting minerals and their predicted fractionation factors.